1. Field of the Invention
This invention relates to a new method of synthesizing highly fluorinated aliphatic primary diamines, to novel intermediates useful in the preparation thereof and to the preparation of said intermediates.
2. Description of the Prior Art
Most highly fluorinated amines and diamines have been prepared by lithium aluminum hydride reduction of the corresponding amides as described by B. S. Marks and G. C. Schweiker, J. Amer. Chem. Soc., 80, p. 5789 (1958) or by high pressure (1000 psi) catalytic hydrogenation of nitriles as described by E. T. McBee, P. A. Wiseman and G. B. Backman, Ind. and Eng. Chem., 39, p. 415 (1947). The former method often gives highly explosive reaction mixtures, while the latter is inconvenient and involves an additional dehydration step in the synthesis. Both methods proceed in only moderate yield.
Other procedures also have been proposed but have not been altogether successful because of the relatively inert nature of the highly fluorinated starting materials as compared to their hydrocarbon counterparts. As reported by B. S. Marks and G. C. Schweiker, ibid., previous attempts to employ 2,2,3,3,4,4-hexafluoropentane-1,5-di-p-toluenesulfonate with ammonia and aliphatic amines, such as methylamine and diethylamine, gave only tarry mixtures from which no amine could be isolated. In one instance, as reported by H.A. Brown and G. V. D. Tiers, J. Org. Chem., 22, p. 454 (1957), reaction of 1,1-di-H-hepta-fluorobutyl p-toluenesulfonate with aniline at 230.degree. C. for 24 hours gave a 68% by weight yield of the desired amine, but reaction under similar conditions with ammonia and diethylamine gave only tars from which the desired products could not be isolated.
In one aspect, the present invention is concerned with a new method of preparing highly fluorinated aliphatic diamines. In another aspect, the present invention is concerned with novel intermediates useful in preparing said diamines and with the synthesis of said intermediates.